We were told 2 more were due too arrive in "late April" but they never turned up. Quite possibly it could be that delivery flight running late? Otherwise only the original pair I mentioned ZM325 and ZM326 are resident at Valley, still undergoing maintenance familiarity and engine runs over on the old SAR/ 22 Sqn PAN.

Believe you me there are quite a few itchy camera trigger fingers waiting to photograph them!

It has been more than two months since the U.S. Air Force’s T-6 Texan II fleet resumed flying operations after a February stand-down that halted all pilot-training flights for almost four weeks, but aircrew are still reporting dangerous, unexplained physiological episodes (UPE) in the cockpit. And the service still has no idea why.

The Air Force has grounded the T-6s twice in the past six months due to UPEs, first from Nov. 15-Dec. 5, 2017, and then again from Jan. 31-Feb. 27. Although both times the aircraft returned to the skies after just a few weeks, investigators still cannot pinpoint a root cause. Since the most recent grounding, T-6 aircrew have reported 14 UPEs, Maj. Gen. Gen. Patrick Doherty, commander of Air Education and Training Command’s (AETC) 19th Air Force unit, told Aviation Week May 1.

In a move that reflects a renewed sense of urgency, AETC Chief Lt. Gen. Steven Kwast in April established a safety investigation board (SIB) to look into the T-6 events. It is headed by Maj. Gen. Michael Rothstein, vice commander of Air University at Maxwell AFB, Alabama.

USAF in April stood up a safety investigation board to look into the events
No root cause has been found
New USAF policy allows pilots to fly with masks down or disconnected from OBOGS T-6s limited to 18,000 ft. and 5gs
T-6s limited to 18,000 ft. and 5g
The SIB will include “more comprehensive” testing of the aircraft system in its entirety, rather than individual components, Doherty says. When asked if the Air Force has any concrete leads, he deferred to the results of the SIB.

“We are concerned that we don’t understand what is going on, and we want to bring more insights into this area,” he says.

This is not the first time the Air Force has tried to get to the bottom of the T-6 problem. During the March stand-down, Air Force Materiel Command chief Gen. Ellen Pawlikowski directed an independent review board to conduct a thorough inspection of the entire breathing system—from the engine bleed air port to the pilot’s mask—on all 444 T-6s. They found several problematic issues with the system, including excess moisture in the condensers and sticky valves. The team was fixing those issues and reevaluating how often certain components of the breathing system should be replaced in maintenance, Pawlikowski said at the time.

The Air Force has now swapped out more than 1,000 components of the T-6, Doherty says.

But despite the efforts, UPEs continue. While no root cause has been identified, several steps have been taken to try to mitigate the problem. These include implementing new inspection procedures, purchasing new testing and monitoring equipment, improving maintenance and educating pilots on how to respond to inflight physiological incidents.

T-6 aircraft
After two standdowns in the last six months, top Air Force officials say T-6 pilots are now recognizing hypoxia-like symptoms sooner and immediately calling an end to the mission. Credit: Zachary Heal/U.S. Airfare

The good news is that pilots are now recognizing the hypoxia-like symptoms much sooner and immediately calling an end to the mission, Doherty says.

Most recently, the 19th Air Force in late April instated a new policy allowing pilots to fly with masks down or disconnected from the Onboard Oxygen Generation System (OBOGS), enabling them to breathe the ambient cockpit air instead of air generated by the OBOGS. However, only a small percentage of pilots are taking advantage of the new policy because of high levels of “trust” in the aircraft, he notes.

In addition, the T-6s are limited to 18,000 ft. and 5gs, but these restrictions are not slowing down the training schedule at all, Doherty notes.

“It’s business as usual,” he says. “Actually, we had a good bit of good weather and so we are actually catching up on the time line.”

As T-6 pilots were continuing normal training operations, the SIB began its work on April 27 with flight tests out of Edwards AFB, California. Unlike previous investigations, the SIB will look into the “man-machine interface,” including monitoring flow pressure and oxygen content flowing into and out of the system, Doherty says. The testing will take place at Edwards and Wright Patterson AFB, Ohio, and will also include laboratory tests.

The goal of the testing, he says, is to characterize “the thresholds of the system, how it operates normally, and [if] there are some areas where they think it deviates from normal operations.”

The SIB comprises experts from the Air Force, U.S. Navy and NASA, Doherty notes.

“They have the processes, the resources and the authorities to bear [the]full weight of [the] effort to try to identify root causes and find our way forward,” he stresses.

Normally an SIB has 30 days to file a report, but given that this particular effort was triggered by a series of incidents rather than one accident or fatality, the time line could be longer, Doherty notes.

He could not say whether investigators will use Cobham’s new VigilOx, a unique, pilot-worn sensor suite that monitors human inhalation and exhalation in real time. The sensors assess the air entering and exiting the pilot’s body for changes in pressure, humidity, temperature, oxygen concentration, flow rate, carbon dioxide—anything that might cause hypoxia-like symptoms.

Separately, NASA is procuring four VigilOx units for a study on fighter-pilot breathing. The sensor recently flew three test flights on the U.S. Navy’s F/A-18 Hornet and T-45 Goshawk trainer, but the services have been slow to adopt the technology.

Discuss this Article (not deleted as quite informative/constructive for a change...TombsRIP)marklincoln1@aol.com on May 10, 2018
The problem is not just constrained to the T-6. Other aircraft using the Onboard Oxygen Generation System have the same or similar problem(s). A seeming brilliant idea, the OBOGS seems to have a problem or two, perhaps three. As the basic problem of oxygen supply at altitude was first confronted a hundred years ago during World War One, and met with moderate success by compressed oxygen and later liquid oxygen, we must ponder technology. Oxygen equipment was drastically improved during World War Two and essentially perfected in the 1950s. But a great idea came along. Replace that old fashioned oxygen bottle and regulator with a spiffy new and shiny albeit complex "Onboard Oxygen Generation System"! Then the problems began.
"The parts you leave off cost nothing and give no trouble."
- Charles Kettering, Engineer of note
jimbo0117 on May 10, 2018
The desire to develop OBOGS was not random - bottled oxygen systems have mission duration limitations compared to what OBOGS provides.marklincoln1@aol.com on May 11, 2018
Take your choice, time limits or dead pilots and wrecked airplanes.trojan5911@yahoo.com on May 10, 2018
I wonder if anyone has bothered to contact the British RAF or the Canadian AF, or for that matter the Swiss who fly a similar Pratt & Whitney powered aircraft to see if they experienced similar problems.
The BAE Hawk is a very popular aircraft as is the Pilatus PC 7/9 and the very similar Tucano/Textron.
Both aircraft are in the USAF inventory and experiencing problems.
but other nations operating these aircraft are not.
Kettering is correct in his assessment that the OBOGS system is the problem. What is so hard to figure out. Why is the OBOGS system is these aircraft experiencing the problem and not the older USAF or USN aircraft? What does the manufacture have to say. Did DOD/USAF make changes that have compromised the system.
This has been a long on going problem. It seems odd that they don't have a grip on it. The US Navy must be smiling.not1star@aol.com on May 10, 2018
Why do I have the feeling that it is something so obvious everyone is overlooking it. That said I assume that blood tests were taken from those affected - for obvious reasons. Is there a chance that these are not random, but actually an act of sabotage aimed at creating disruptions to complicate training, operations, and confidence the systems. If I were to suggest something - take the aircraft affected, the crews affected and run the plane on the ground to also see if there are positive results. Or do this in the air with a second pilot on a stand alone oxygen system for test flights. Or, why not just have an stand alone as a back up which would allow pilots to descend to safe altitudes and let some "fresh air" into the cockpit. Just thoughts to try and help - just consider and don;'t toss them out without some consideration from a third party.
QuestionMark on May 10, 2018
Is the OBOGGS software-controlled?
price.bob.e@gma... on May 10, 2018
Perhaps they should include CDC, which seems really good at finding system roots for problems.
capngrog on May 10, 2018
Are aircraft involved in a UPE (Unexplained Physiological Episode) incident sent back up, unchanged, with a pilot completely outfitted with monitoring gear (blood O2 etc.) to see if the Physiological Episode can be duplicated? Of course, a second pilot, breathing from a LOX system, would be required to take over if the OBOGS-breathing pilot experienced a UPE.